Chemical vapor deposition methods are employed to form films of material on substrates such as wafers or other surfaces during the manufacture or processing of semiconductors. In chemical vapor deposition, a chemical vapor deposition precursor, also known as a chemical vapor deposition chemical compound, is decomposed thermally, chemically, photochemically or by plasma activation, to form a thin film having a desired composition. For instance, a vapor phase chemical vapor deposition precursor can be contacted with a substrate that is heated to a temperature higher than the decomposition temperature of the precursor, to form a metal or metal oxide film on the substrate. Preferably, chemical vapor deposition precursors are volatile, heat decomposable and capable of producing uniform films under chemical vapor deposition conditions.
The semiconductor industry is currently considering the use of thin films of various metals for a variety of applications. Many organometallic complexes have been evaluated as potential precursors for the formation of these thin films. A need exists in the industry for developing new compounds and for exploring their potential as chemical vapor deposition precursors for film depositions. Current aluminum precursors for chemical vapor deposition suffer from a number of shortcomings including high viscosity, low stability, pyrophoric nature, low vapor pressure and high cost.
U.S. Pat. No. 5,880,303 discloses volatile, intramolecularly coordinated amido/amine alane complexes of the formula H2Al{(R1)(R2)NC2H4NR3} wherein R1, R2 and R3 are each independently hydrogen or alkyl having 1 to 3 carbon atoms. It is stated that these aluminum complexes show high thermal stability and deposit high quality aluminum films at low temperatures. It is also stated that these aluminum complexes are capable of selectively depositing aluminum films on metallic or other electrically conductive substrates. However, these aluminum complexes are either solids or high viscosity liquids at room temperature.
Alumina (Al2O3 or aluminum oxide) thin films are utilized by the semiconductor industry for applications requiring chemical inertness, high thermal conductivity and radiation resistance. They are used in the manufacture of liquid crystal displays, electroluminescent displays, solar cells, bipolar devices and silicon on insulator (SOI) devices. In addition, alumina is a wear resistant and corrosion resistant coating used in the tool making industry. Most aluminum chemical vapor deposition precursors are pyrophoric which makes them difficult to handle. Those that are not pyrophoric, such as amine-alanes, suffer from short shelf life and high viscosity and low vapor pressure. It would be desirable to develop a non-pyrophoric alumina precursor that had a low viscosity, high vapor pressure and long shelf life.
In developing methods for forming thin films by chemical vapor deposition or atomic layer deposition methods, a need continues to exist for precursors that preferably are liquid at room temperature, have adequate vapor pressure, have appropriate thermal stability (i.e., for chemical vapor deposition will decompose on the heated substrate but not during delivery, and for atomic layer deposition will not decompose thermally but will react when exposed to co-reactant), can form uniform films, and will leave behind very little, if any, undesired impurities (e.g., halides, carbon, etc.). Therefore, a need continues to exist for developing new compounds and for exploring their potential as chemical vapor or atomic layer deposition precursors for film depositions. It would therefore be desirable in the art to provide a precursor that possesses some, or preferably all, of the above characteristics.